early 15c., from Middle French desloyaulte, from Old French desloiaute, desleauté "disloyalty, faithlessness, marital infidelity," from desloial (see disloyal). Especially of allegiance to a state or sovereign since c.1600.

Through the Middle Ages, calendars marked two days of each month as unlucky, supposedly based on the ancient calculations of Egyptian astrologers (Jan. 1, 25; Feb. 4, 26; March 1, 28; April 10, 20; May 3, 25; June 10, 16; July 13, 22; Aug. 1, 30; Sept. 3, 21; Oct. 3, 22; Nov. 5, 28; Dec. 7, 22). Modern sense of "gloomy, dreary" first recorded in English 1590s, in reference to sounds. Related: Dismally.

late 13c., dismaien, from Old French *desmaier (attested only in past participle dismaye), from Latin de- intensive prefix + Old French esmaier "to trouble, disturb," from Vulgar Latin *exmagare "divest of power or ability" (source of Italian smagare "to weaken, dismay, discourage"), from ex- (see ex-) + Germanic stem *mag- "power, ability" (cognates: Old High German magen "to be powerful or able;" see may (v.)). Spanish desmayer "to be dispirited" is a loan word from Old French. Related: Dismayed; dismaying.

early 15c., dysobedyent, from Old French desobedient, from Vulgar Latin *disobedientem (replacing Latin inobedientem) from Latin dis- (see dis-) + obedientem (see obedient). Related: Disobediently. Earlier in the same sense was disobeissant (late 14c.), from Old French desobeissant, and inobedient (early 14c.).

late 14c., from Old French desobeir (13c.) "disobey; refuse service or homage," from Vulgar Latin *disoboedire, reformed with dis- from Late Latin inobedire, a back-formation from inobediens "not obeying," from Latin in- "not" + present participle of obedire (see obey). Related: Disobeyed; disobeying.

1580s, "opposed to moral order," also "opposed to legal authority;" see dis- + orderly (adj.). The meaning "untidy" is attested from 1630s; the older senses are those in disorderly house, disorderly conduct, etc.

1793, from French désorganiser, from dés- "not" (see dis-) + organiser "organize" (see organize). This word and related forms were introduced in English in reference to the French Revolution. Related: Disorganized; disorganizing; disorganization.

1510s, "to send off in a hurry," from a word in Spanish (despachar "expedite, hasten") or Italian (dispacciare "to dispatch"). For first element, see dis-. The exact source of the second element has been proposed as Vulgar Latin *pactare "to fasten, fix" or *pactiare, or as Latin -pedicare "to entrap" (from Latin pedica "shackle;" see impeach); and the Spanish and Italian words seem to be related to (perhaps opposites of) Old Provençal empachar "impede." See OED for full discussion. Meaning "to get rid of by killing" is attested from 1520s. Related: Dispatched; dispatching. As a noun, from 1540s, originally "dismissal;" sense of "a message sent speedily" is first attested 1580s.

c.1400, dispelen, from Latin dispellere "drive apart," from dis- "away" (see dis-) + pellere "to drive, push" (see pulse (n.1)). Since the meaning is "to drive away in different directions" it should not have as an object a single, indivisible thing (you can dispel suspicion, but not an accusation). Related: Dispelled; dispelling.

late 14c., from Old French despensacion (12c., Modern French dispensation), or directly from Latin dispensationem (nominative dispensatio) "management, charge," noun of action from past participle stem of dispensare (see dispense). Theological sense is from the use of the word to translate Greek oikonomoia "office, method of administration."

In Medieval Latin, dispendere was used in the ecclesiastical sense of "grant license to do what is forbidden or omit what is required" (a power of popes, bishops, etc.), and thus acquired a sense of "grant remission from punishment or exemption from law," hence "to do away with" (1570s), "do without" (c.1600). Older sense is preserved in dispensary. Related: Dispensed; dispensing.